Judgments of voice quality contribute greatly to patients' opinions of their voice, and also to a clinician's decision to initiate and continue treatment. Quality judgments are further used as a standard against which instrumental measures of voice are validated. Nevertheless, these "subjective" measures of voice quality are not highly regarded as either clinical or research tools, because of problems with reliability and untested validity. We hypothesize that problems in voice quality measurement do not originate within the listener, but rather derive from the methods used to measure what listeners hear. The proposed research departs from these traditional rating scale methods by applying a speech synthesizer for pathological voice quality to study fundamental issues concerning reliability and validity of measures of voice quality. In this approach, listeners an asked to adjust synthesizer parameters to achieve a perceptual match to the original voice -- to "rate" a voice by matching it. This method explicitly links the acoustic signal to perceived voice quality. The investigators hypothesize that this linkage across the speech chain increases the validity, reliability, and utility of both acoustic and perceptual representations, by providing listeners with an objective tool (a synthesizer) for quantifying what they hear. The proposed research focuses on expanding and refining our synthesizer for pathological voice quality, compares the validity and reliability of synthesis techniques to traditional rating scale techniques for evaluating voice quality, applies the synthesizer to examine the perceptual importance of a periodicity, noise and the shape of the voicing source pulse, and quantifies the different sources of error in voice quality measurement. The investigators hypothesize that the protocols described here will greatly increase both the reliability and validity of voice quality measurement, bringing us much closer to our goal to develop a standardized voice evaluation protocol.